Regarding Subroutine

Hi all

 i am new user of Abaqus and as a part of my research i need to define a subroutine for composite plate delamination during drilling.however, i still dont know how to open a subroutine file to write in Fortran language? how can i see the available subroutine files as a guidance? i will appreciate if any one answer to help me by answering my question.

thanks